A DIFFERENT APPROACH TO LOW FORMALDEHYDE EMISSION AMINOPLASTIC WOOD ADHESIVES

Melamine-formaldehyde resins prepared with a molar defect of formaldeh yde (i.e. molar ratio M : F = 1:0.5) were shown to harden in presence of hexamethylenetetramine, at acid pH. without a great proportion of d ecomposition of hexamethylenetetramine to formaldehyde. Approximately 2/3 of the cross-linking bridges induced by hexamethylenetetramine har dening appear to be stable aminodi- and aminotrimethylene bridges deri ved by reaction of Hultzsch methylene bases directly with reactive sit es on melamine and on the MF resin. This confirms that hexamethylenete tramine is capable of reacting also with aminoplastic resins mostly be fore its degradation to formaldehyde. The existence of such a type of cross-linking was shown to lead to hardened aminoplastic resins capabl e of much lower formaldehyde emission from the finished board.